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The fundamental trade-off between current and future reproduction has long been considered to result in a tendency for species that can grow large to begin reproduction at a larger size. Due to the prolonged time required to reach maturity, estimates of tree maturation size remain very rare and we lack a global view on the generality and the shape of this trade-off. Using seed production from five continents, we estimate tree maturation sizes for 486 tree species spanning tropical to boreal climates. Results show that a species' maturation size increases with maximum size, but in a non-proportional way: the largest species begin reproduction at smaller sizes than would be expected if maturation were simply proportional to maximum size. Furthermore, the decrease in relative maturation size is steepest in cold climates. These findings on maturation size drivers are key to accurately represent forests' responses to disturbance and climate change.

Arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) associations are critical for host-tree performance. However, how mycorrhizal associations correlate with the latitudinal tree beta-diversity remains untested. Using a global dataset of 45 forest plots representing 2,804,270 trees across 3840 species, we test how AM and EcM trees contribute to total beta-diversity and its components (turnover and nestedness) of all trees. We find AM rather than EcM trees predominantly contribute to decreasing total beta-diversity and turnover and increasing nestedness with increasing latitude, probably because wide distributions of EcM trees do not generate strong compositional differences among localities. Environmental variables, especially temperature and precipitation, are strongly correlated with beta-diversity patterns for both AM trees and all trees rather than EcM trees. Results support our hypotheses that latitudinal beta-diversity patterns and environmental effects on these patterns are highly dependent on mycorrhizal types. Our findings highlight the importance of AM-dominated forests for conserving global forest biodiversity.

Spatial variability of humus properties in a natural fir-beech forest was studied along with the influence of windthrows and mesorelief on this variability. In 1720 windthrows the thickness and form of the organic horizons were studied in three positions--mound, pit, and undisturbed control. On undisturbed sites, substantial variability of thickness and forms of the organic horizons was found on a fine scale (0-10 m). Close spatial dependence of some humus characteristics was found on a coarser scale (20-120 m). The mesorelief was found to be one of the key autocorrelation factors. The level of spatial dependence was not uniform; it differed between the fermented and humification horizons and among their forms. The presence of windthrows increased the variability of humus thickness on both fine (0-10 m) and coarse (level of entire locality, i.e., 11 ha) scales. However, windthrows did not increase the variability of organic horizon forms (OHFs) on a fine scale. High variability of OHFs is probably a property of fully developed mature humus in a natural firbeech forest. On a coarse scale, the presence of pits increased the frequency of fermented zoogenous and humification residual horizons on the study area. La variabilite spatiale des proprietes de l'humus dans une foret naturelle composee de sapin et de hetre a ete etudiee en fonction de l'influence des chablis et du mesorelief. Dans 1720 chablis, l'epaisseur et la forme des horizons organiques ont ete etudiees dans trois positions : les monticules, les depressions et les temoins non perturbes. Sur les stations non perturbees, nous avons observe une variation substantielle de l'epaisseur et de la forme des horizons organiques a une echelle fine (0-10 m). Une dependance spatiale etroite a ete detectee entre les caracteristiques de l'humus a une echelle plus grossiere (20-120 m). Le mesorelief etait un des facteurs cles de cette autocorrelation. Le degre de dependance spatiale n'etait pas uniforme puisqu'il etait different entre les horizons fermentes et humifies et entre leurs formes. La presence de chablis augmentait la variabilite de l'epaisseur de l'humus aux echelles fine (0-10 m) et grossiere (echelle d'une localite entiere, c.-a-d. 11 ha). Cependant, les chablis n'ont pas augmente la variabilite de la forme des horizons organiques a une echelle fine. Une forte variabilite de la forme des horizons organiques est probablement caracteristique d'un humus mature, completement developpe, dans une foret naturelle composee de sapin et de hetre. A une echelle grossiere, la presence de depressions a augmente la frequence des horizons zoogenes fermentes et des horizons residuels humifies dans l'aire d'etude. [Traduit par la Redaction], Introduction The forest floor of natural forest ecosystems results from interactions of the biocenosis, soil environment, and atmosphere. The high number of biological mechanisms present leads to high spatial variability [...]

Fagus sylvatica (European beech) populations in Central Europe are currently expanding their dominance in many forest types. In this study we focused on the spatio-temporal dynamics of beech recruitment as a mechanism for successful expansion. Specifically we investigated: (1) the developmental trend of the tree community composition and spatial pattern in an unmanaged Picea abies-F. sylvatica forest over 37 years, (2) the pattern of decrease in clustering along increasing tree size gradient of beech, and (3) the spatial patterns of beech regeneration in relation to gap-makers. The study was conducted in the Žofín Forest Dynamics Plot, which is part to the Smithsonian Institution’s Forest Global Earth Observatory (ForestGEO) as the research plot representing European natural mixed temperate forests. To quantify these dynamics, we used the stem map of trees with DBH ⩾ 10 cm carried out in 1975, 1997, 2008 and a census of trees with DBH ⩾ 1 cm from 2012 to calculate recruitment, growth, mortality and, from those vital rates, population change. Various types of the pair correlation function were applied to the data to describe the tree density variability over time. Our analyses revealed a trend of increasing F. sylvatica representation at the expense of P. abies and Abies alba over the 37 years. Increased clustering of F. sylvatica trees with DBH ⩾ 10 cm correlated with new recruits at plots where F. sylvatica replaced declining P. abies . On the other hand, the decrease in F. sylvatica clustering at some plots was likely due to strong intra-specific competition. The analysis of the spatial patterns of F. sylvatica individuals along DBH gradient 1–9 cm showed a trend of increasing clustering up to 5 m distance. F. sylvatica saplings to 4 cm of DBH were positively spatially correlated with other conspecific individuals, although at larger sizes (DBH 7–9 cm), this relationship reversed to a negative correlation. Analysis of relationships between saplings and gap-makers did not reveal a clear pattern. We concluded that without a coarse-scale disturbance capable of restructuring the community, F. sylvatica will become the only dominant tree species in this forest type. F. sylvatica gradually replaces P. abies through its space occupation strategy because its recruits are already present before a canopy disturbance. Our results indicate that F. sylvatica saplings can grow up to 4 cm DBH under a closed canopy, but require a canopy disturbance to advance to a larger size class. [ABSTRACT FROM AUTHOR]

European beech ( Fagus sylvatica ) increases its dominance in various forest types in Central Europe. In this context we investigated a very exceptional process, in which beech have been partly outcompeted by sycamore maple ( Acer pseudoplatanus ) in unmanaged forest without severe disturbances. Main research questions were as follows: (i) How did the spatial patterns of beech and sycamore develop, and can these patterns be described by known spatial models?; (ii) What were the spatial relationships between beech and sycamore?; (iii) Does the spatial relationship of advance regeneration to gap-makers differ for the two species?; (iv) Did the presence of a road influence the spread of the sycamore population? The study was conducted in beech-dominated forest Žákova hora in the central part of the Czech Republic which has been left to spontaneous development for 85 years. We studied long-term forest dynamics using stem position maps of trees with DBH ⩾ 10 cm carried out in 1974, 1995 and 2011. We used standard methods for calculating recruitment, mortality and population change. Various types of the pair correlation function were applied to describe the development of tree spatial patterns. Our results showed that sycamore regenerated in the close vicinity of other conspecific trees. Sycamore recruits were not spatially associated to individual gap makers. Sycamore individuals had a highly clustered distribution, and the number of individuals grew mostly through the increasing of existing clusters. We successfully fitted the Matérn cluster process for sycamore spatial patterns. The radius of the model cluster ranged between 6 and 16 m. By contrast, beech recruits were negatively correlated to older conspecific trees and showed independence or positive correlation to sycamore veterans. The vicinity of the road significantly promoted sycamore recruitment (opposed to the beech). If the sycamore expansion is connected with the vicinity of the road and thickening of existing sycamore clusters only, as our results indicate, then it can be spatially and temporally limited process. [ABSTRACT FROM AUTHOR]

Natural disturbance regimes play key roles in shaping forest structure and development at stand and landscape levels. Disturbances are commonly complex and variable, such that classical dichotomous characterization of disturbance regimes as following large infrequent disturbances or patch dynamics is too simplistic, especially when the resulting damage is more severe than the baseline of a single tree patch dynamic, but not severe enough to represent large infrequent disturbance. Ongoing climate change affects mountain Picea abies forests in Central, East and Southeastern Europe by an increasing frequency of storms and bark beetle outbreaks. We present a unique study based on extensive dataset aimed to reveal the spatiotemporal pattern of the disturbance history and role of the mixed severity disturbances in primary spruce mountain forest landscapes in the Ukrainian Carpathians. We reconstructed canopy disturbance history and maximum disturbance severity using ca. 2396 tree cores in 96 sample plots. Neither large-scale stand-replacement nor fine scale dynamics was the prevailing disturbance over the last four centuries. Rather, we observed a complex spatiotemporal pattern of mixed severity disturbances. Canopy turnover time ranged between 50 and 300 years and depended on the maximum severity of the disturbance event. Spatial analyses revealed no similarity in spatiotemporal pattern across disturbance histories or maximum disturbance severities. We observed evidence of a combination of variable severity disturbances that fails to fit the classical scheme of gap or patch dynamics with sharply defined sizes and borders, but is more consistent with a mixed severity disturbance regime across the landscape. Windstorms were likely the most important past disturbance agent. The probability of an epidemic bark beetle attack was low, although the possibility of small local outbreaks cannot be excluded. An additional, potentially overlooked, agent of disturbance could be historic periods of extreme cold. This reconstructed disturbance regime may challenge existing silvicultural systems in the Carpathians, calling for a more complex spatiotemporal forest management approach. However, mimicking a mixed severity disturbance regime can be done at the forest management level by applying a range of disturbance severities at the stand level. [ABSTRACT FROM AUTHOR]

This paper presents the correlations between two different analytical methods of assessing soil nutrient contents. Soil nutrient content measurements measured using the flame atomic absorption spectrometry (FAAS ) method, which uses barium chloride extraction, were compared with those of the now-unused Gedroiz method, which uses ammonium chloride extraction (calcium by titration, magnesium, potassium and sodium by weighing). Natural forest soils from the Ukrainian Carpathians at the localities of Javorník and Pop Ivan were used. Despite the risk of analysis errors during the complicated analytical procedure, the results showed a high level of correlation between different nutrient content measurements across the whole soil profile. This allows concentration values given in different studies to be linearly recalculated on results of modern method. In this way, results can be used to study soil’s chemical changes over time from the soil samples that were analysed in the past using labour-intensive and time-consuming methods with a higher risk of analytic error.